Densities and Viscosities of 1-Ethyl-3-methylimidazolium n-Alkyl Sulfates

Density and viscosity data for four 1-ethyl-3-methylimidazolium-based ionic liquids combined with alkyl sulfate, [CnSO4](-) with n = 1, 4, 6, and 8, and hydrogen sulfate, [HSO4](-), anions were measured at atmospheric pressure in the temperature range 283 < T/K < 363. Isobaric thermal expansion coefficients were calculated from the density results. This work studies the effect of increasing the alkyl chain length of the sulfate-based anion on the density, viscosity, and related properties of this family of ionic liquids. The effective volumes of the distinct anions used were calculated from the measured density values, simply by subtracting the effective volume of the cation already available from literature to the molar volume of the ionic liquid. We also evaluated the predictive ability of group contribution methods for density and viscosity. Since large deviations between the predictions and the experimental data occurred for both density and viscosity, new group contribution parameters were proposed. The results dearly show that [HSO4](-) cannot be considered part of the [CnSO4](-) family.